Effects of fire frequency and mowing on a temperate, derived grassland soil in south-eastern Australia

2008 ◽  
Vol 17 (5) ◽  
pp. 586 ◽  
Author(s):  
Suzanne M. Prober ◽  
Ian D. Lunt ◽  
Kevin R. Thiele

Frequent disturbances such as fire are widely considered important drivers of plant composition and diversity in productive grassy ecosystems. Effects of fire frequency on grassland soils, however, are less well understood. We established replicated disturbance regimes in a high-quality, representative Themeda australis–Poa sieberiana-derived grassland in south-eastern Australia that had historically been burnt every 4–8 years. Effects on soil chemical, physical and biological properties were measured after 10 years of application of 2-, 4-, and 8-yearly burning, 2-yearly mowing and an undisturbed treatment. Contrary to other grassy ecosystems, there were no detectable effects of disturbance regime on total soil nitrogen and carbon, or a range of other soil chemical properties in the top 10 cm. However, a cumulative effect of burning on the grassland soil was evident from a suite of changes to soil surface properties, available nutrients and biological activity. In particular, on biennially burnt plots, reduced litter and plant protective cover were associated with increased soil surface compaction, decreased infiltration and decreased soil biological activity, which in turn were related to poor sward recovery after fire and drought. These relationships indicate potential for positive feedbacks whereby repeated removal of soil protective cover and changes to soil surface chemistry through very frequent burning ultimately lead to further reduction in soil protective cover through reduced productivity. However, this is only likely in extreme cases: data from unburnt plots indicated that soils that had historically been burnt every 4–8 years had not passed a threshold beyond which such soil changes were irreversible or damaging. Contrary to other predictions, cessation of burning for 13 years did not lead to detectable soil nutrient release through senescence of dominant grasses. Biennial mowing with slash retention was an effective alternative disturbance for maintaining sward vigour while avoiding soil surface damage.

2014 ◽  
Vol 62 (5) ◽  
pp. 369 ◽  
Author(s):  
Annette M. Muir ◽  
Peter A. Vesk ◽  
Graham Hepworth

Intervals between fires are critical for the persistence of obligate-seeding shrubs, and are often used in planning fires for fuel reduction and biodiversity conservation in fire-prone ecosystems worldwide. Yet information about the trajectories of reproductive performance for such species is limited and information is often qualitative. To test existing assumptions about reproductive maturity periods for eight obligate-seeding shrubs (with both canopy and soil seedbanks) in foothill forests of south-eastern Australia, we used a chronosequence approach, with sites from 2 years to >40 years post-fire. Quantitative measurements of flowering and fruiting were used to fit models of reproductive response in relation to time-since-fire for each species. Inferred reproductive maturity for each species, based on modelled times to reach 80% of maximum flower production, varied from 5 to 18 years post-fire. For a subset of three species, models predicted 80% maximum seed production occurring 1–7 years later than flowering. Our results confirmed or extended assumptions about post-fire reproductive maturity for these species, and provided a basis for improved incorporation of plant life-history in ecological fire planning. We infer that increased fire frequency makes one of our study taxa, Banksia spinulosa var. cunninghamii (Sieber ex Rchb.) A.S.George, vulnerable to decline because of its long reproductive maturity period and serotinous seed storage.


2003 ◽  
Vol 43 (10) ◽  
pp. 1231 ◽  
Author(s):  
S. J. Marcroft ◽  
S. J. Sprague ◽  
S. J. Pymer ◽  
P. A. Salisbury ◽  
B. J. Howlett

The production of windborne ascospore inoculum of the blackleg fungus (Leptosphaeria maculans) was determined during 2000 and 2001 in 3 environments (Birchip, low rainfall; Wonwondah, medium rainfall; Lake Bolac, high rainfall) in Victoria. The weight of canola stubble (kg/ha) remaining on the soil surface in paddocks was estimated 6, 18, 30 and 42 months after harvest of the original canola crop. In all 3 environments only small amounts of stubble were present 18 months after harvest. Eighty percent of the 6-month-old stubble comprised stems and branches, with the remaining 20% being root material, while 42-month-old stubble consisted only of root material. Paddocks subjected to raking and burning contained only half the weight of stubble compared with paddocks that were harrowed. Where canola was harvested in January, even when no management strategy was used, 80% of subsequent stubble was no longer on the soil surface by July of that year. Pseudothecia from 6-month-old stubble from the high rainfall environment discharged significantly more ascospores than stubble of the same age from the medium rainfall environment, which in turn discharged more than stubble from the low rainfall environment. In all environments, paddocks containing 6-month-old canola stubble discharged 30-fold as many ascospores per hectare as older stubble paddocks.


1972 ◽  
Vol 20 (2) ◽  
pp. 197 ◽  
Author(s):  
RW Rogers ◽  
RT Lange

Lichens on soils in Australia have been neglected until recently. This paper describes a study area of nearly 1 million km2 in south-eastern Australia, and the methods used to determine the lichens found on the soil surfaces in that area. In all, 343 locations were examined, 227 of which had soil surface lichens. From the range of lichens encountered a total of 42 taxa were delimited, and in 36 cases ascribed to previously described species or complexes; the remaining six were either un- described, or depauperate forms which could not be placed. The world phytogeographic implications of this study are discussed.


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